1. Field of the Invention
The present invention relates to thermoforming machines, and particularly to a thermoforming machine which can be installed with various molds for forming a flat film onto a shaped mold.
2. Discussion of the Related Art
A traditional technology to decorate the plastic components is using post-molding techniques, including airbrushing, pad printing, painting, etc. However, these decorating methods are time-consuming, and the resulting appearance is poor. Therefore, in mold decoration (IMD) has been developed to decorate plastic components. A first decorating film is placed in a mold cavity in which the product is to be formed. A molten material is then injected into the mold cavity. The decorative film is attached to the surface of the molded product after a mold cavity containing the decorative film is injection molded. Thus, the decorative film needs to be accurately placed into position so that the decoration thereof is aligned with the intended location on the product. The product is then molded in contact with the decorative film. After cooling, the product with the decorative film is removed from the mold, thereby completing the fabrication of the product.
However, the IMD process has a number of drawbacks. Firstly, IMD film cannot be preformed, and hence it is limited to flat or only slightly shaped products. Secondly, IMD product design geometry is limited. When either side of a core or a cavity insert is higher than the parting line, the film will squeezed and IMD can not be applied. Thirdly, IMD film has a release carrier which needs to be removed.
In mold labeling (IML) is an improved technique for decorating a plastic parts. It starts with a high precision printed plastic film that goes through a pre-forming process to form a three-dimensional (3D) film. The 3D film is then trimmed of its excess material to match a molded product. Then, the 3D film is placed in a mold cavity of a mold machine, and fuse together with the molten material injected into the cavity. The most critical part of IML is in the thermoforming or pre-forming process of the decorating film. Conventional thermoforming process for flat films includes vacuum forming, pressure forming, hydro forming, and matched metal forming. The cheapest of these methods is matched metal forming. Matched metal forming generally uses gas or pressurized hydraulic fluid as a driving force. However, it is a difficult to precisely control process which can result in deformation of the pre-forming film because of speed at which the film is stretched.
What is needed, therefore, is a thermoforming machine which overcomes these problems.